Carrageenan is a natural hydrocolloid, more particularly a polysaccharide hydrocolloid, which is derived from edible red seaweed, particularly of the species Rhodophyceae. Carrageenan is a carbohydrate polymer of repeating galactose and 3,6-anhydrogalactose (sugar) units that is linear and without significant numbers of branches or substitutions. Most, if not all, of the galactose units on a carrageenan molecule possess a sulfated ester group. The exact position of the sulfate groups, the cations on the sulfate groups, and the possible presence of an anhydrous bridge on the molecule differentiate the various types of carrageenan. The molecules are large and highly flexible and can form helical structures. This gives them the ability to form gels at ambient temperatures.
A need has arisen in recent years for gelatin-alternatives for soft capsule manufacturing. This need was driven primarily by the identification of Bovine Spongiform Encephalitis (BSE) in cattle, a primary source of gelatin used in soft capsules. In addition, vegetarians and consumers with religious restrictions on consuming materials of animal origin have further heightened the need to develop animal-free soft capsules. Animal-free soft capsules have been developed as described in International Patent Application Publication No. WO 2005/004840 and U.S. Pat. Nos. 6,214,376; 6,949,256; and 7,887,838, each of which is fully incorporated by reference herein for such teachings. While such soft gel technologies are useful for gastric delivery, there remains a need for an enteric non-gelatin soft capsule technology.
Accordingly, it is desirable to develop an enteric soft capsule that comprises carrageenans as film-forming agents in place of gelatin. This permits the manufacture of animal-free enteric soft capsules.